1. Field of the Invention
The present invention relates to the field of power supplies, and more particularly to detecting a malfunction of a slave power supply and triggering an interlock signal in response to the detection of the malfunction.
2. Description of the Relevant Art
As defined herein, a xe2x80x9cpower supplyxe2x80x9d is a device for the conversion of available power of one set of characteristics to another set of characteristics to meet specified requirements. In a typical application of a power supply, raw input power available in the form of 110V AC or 220V AC is converted to a controlled or stabilized voltage. A power supply system may include a number of power supplies coupled together. Examples of electrical parameters, properties or characteristics which are typically specified for a power supply may include output power, output voltage, output current, input voltage, input current, percent regulation, ripple effect, load impedance, resolution, and accuracy.
As defined herein a xe2x80x9csignalxe2x80x9d is a detectable and measurable physical quantity or impulse (such as a voltage, current, or power) by which messages or information can be transmitted from a source to a destination. For example, a signal representing a characteristic of a power supply, e.g., voltage, is measured in terms of a value and a measurement unit, e.g., 110 Volts AC. Power supplies play a vital role in the field of semiconductor manufacturing, where a power supply system is required to deliver voltages of up to 1500 volts for sputtering in thin film processing. Predictability, reliability, repeatability and cost are critical in an application such as this, where a malfunction in a power supply may result in the stoppage of a production line. The production loss and the subsequent rework may cost millions of dollars in lost profits. The following U.S. patents, which discuss various applications of power supplies, are hereby incorporated herein by reference: Apparatus for Removal of Electrical Shorts in a Sputtering System (U.S. Pat. No. 5,009,764), Method for Removal of Electrical Shorts in a Sputtering System (U.S. Pat. No. 4,963,238), Method and Apparatus for Recovery from Low Impedance Condition during Cathodic Arc Processes (U.S. Pat. No. 4,963,238), Topographically Precise Thin Film Coating System (U.S. Pat. No. 6,120,656), and Auto-ranging Power Supply (U.S. Pat. No. 6,011,704). The electrical power demand for sputtering in a aluminum chamber may require two power supplies. Referring to FIG. 1, a conventional arrangement of two power supplies as a master/slave power supply system 130 is illustrated. The power supply system 130 serves a manufacturing system 100. One example of such a manufacturing system is the Endura(copyright) PVD (physical vapor deposition) system manufactured by Applied Materials, Inc., Santa Clara, Calif. One example of a power supply system is the MDX Series power supply, manufactured by Advanced Energy Industries, Inc., Fort Collins, Colo.
In FIG. 1, the load on the power supply system 130 is shared by a first power supply 110 and a second power supply 120 in a xe2x80x9cmaster/slavexe2x80x9d arrangement, that is, an arrangement in which the first power supply 110 controls the proportion of the load supplied by each one of the respective power supplies 110 and 120. This arrangement may be configurable. For example, the master and the slave power supplies may be configured so that the master power supply 110 splits the load substantially equally with the slave supply 120.
The master-slave power supply system 130 of FIG. 1 is configured in a cascade arrangement, according to which the manufacturing system 100 sends a set point signal 140 to the master power supply 110 to represent an output power demand. This required power is variable since as the manufacturing process requirements change the need for power required by the manufacturing system may vary. For example, if the system 100 detects an impurity in the aluminum chamber the system will demand more power.
The master power supply 110 receives the set point 140 from the manufacturing system 100 and in response regulates its output and/or the set point 150 for the slave power supply 120 output. The slave power supply 120 receives the set point 150 and in response regulates its own output.
In response to the set point 140 received from the manufacturing system 100, the master power supply 110 also sends to the manufacturing system 100 a signal 160 which is an estimate of the combined master-slave power supply output. In the system 130 of FIG. 1, the master power supply 110 always assumes that the slave power supply 120 is able to match the actual power output to the set point 140 received from the master. However, the slave power supply 120 might not be able to deliver the desired power output as specified by the set point 150. This could be due to lack of capacity, for example, or due to some other malfunction. Since, as is illustrated in FIG. 1, there is, at least in some respects, an absence of feedback to the master power supply 110 from the slave 120 to indicate whether the slave power supply 120 has been able to adjust its output to match the set point 150, a malfunction of a slave power supply 120 may not be known to the master. Thus, a need exists to detect a malfunction of a slave power supply 120 and trigger an interlock signal in response to the malfunction. Furthermore, this need is harder to address by a user of a power supply system 130 than it would be by the power supply developer. That is, when an existing power supply system must be retrofitted for detection of the slave power supply malfunction and triggering of an interlock there are more constraints than there would be if detection and interlocking were being designed for a power supply system during development of the system.
The problems outlined above are addressed by a system and method for detecting a malfunction of a slave power supply and triggering an interlock signal in response to the detection of the malfunction, as described herein.
Power supplies may be regulated in a variety of ways. In an embodiment of the present invention, a feedback technique is used, according to which a feedback signal provides information about voltage output to control circuitry of the power supply system. A set point signal establishes a target output level that the control circuitry attempts to maintain. The set point may be established through a manual setting or by a software program, for example. The control circuitry regulates the power supply by comparing the set point to the actual voltage output. A xe2x80x9cmalfunctionxe2x80x9d of the system occurs when the system fails to operate normally. If the control circuitry is not able to regulate the power supply output voltage, for example, this is abnormal and is thus a malfunction of the power supply.
In one embodiment, a master-slave power supply is configured in a cascade arrangement to supply power to a manufacturing system. A manufacturing system responds to the conditions of the manufacturing process by adjusting a set point for demanding a specified output power from the master-slave power supply. In response to receiving the set point from the manufacturing system the master power supply demands an output from the slave power supply such that the combined output power meets the specified output power.
In a first form, a method for activating an interlock signal upon detecting a malfunction of a slave power supply includes receiving a first input from the slave power supply representing the set point for the output power of the slave power supply, and a second input from the slave power supply representing the output power of the slave power supply. According to the method, a determination is made that the slave power supply system has malfunctioned if the received inputs substantially mismatch. In response to the determination of the malfunction, an interlock signal is activated.
In one aspect, the input received for the set point may represent the status of a set point LED on the master power supply. In another aspect, the input received for the output may represent the status of an output LED on the master power supply.
In another form, a system for detecting malfunction of a power supply and activating an interlock includes component based electronic circuits for the detecting and interlocking, according to an embodiment. In one aspect, the system includes a first circuit section and a second circuit section.
In one embodiment, the first circuit section provides the function of malfunction detection and includes an input section, a noise isolation section and a logic control section. The first circuit section is configurable to receive a signal representing the set point for the output power and a signal representing the output power of the slave power supply system. The first circuit section is configurable to activate a trigger signal when the set point signal is not substantially equal to the output signal.
The second circuit section, which is electrically coupled to the first circuit section, is configurable to activate the interlock signal in response to receiving the trigger signal. In one embodiment, the second circuit section provides the function of interlock activation and includes a digital switch section, a time delay section and a interlock trigger section.
In another embodiment, a processor executes program instructions stored in memory to implement at least some aspects of the system or method. According to this embodiment, the system includes a processing unit, memory coupled to the processing unit and a program included in the memory. The program is executable by the processor to implement malfunction detection and interlock triggering logical functions.